fons et origo, n. The source and origin (of something).

clock-calm, n. A state or condition of the sea in which its surface is extremely calm and still.

meatspace, n. The physical world, as opposed to cyberspace or a virtual environment.

nab, v.1 Scottish. To bite gently, to nibble.

foolery, n. An instance of foolish behaviour; a foolish or ridiculous belief, action, or thing.

geosmin, n. An organic compound with a strong earthy scent and flavour, produced especially by various microorganisms and largely responsible for the smell of damp soil.

nincompoopiana, n. (A name for) the late 19th-cent. aesthetic movement; (more generally) the vogue for aestheticism which accompanied it.

mythomaniac, n. A person obsessed with or passionate about myths. Also: a person with a pathological tendency to create myths, tell lies, or exaggerate.

fontlet, n. A small source or wellspring; a little fountain.

OED Word of the Day on World Cake Day: cakelet, n. A small cake.